1. Field of the Invention
The present invention relates to a medicine comprising as an active ingredient a specific .alpha.-galactosylceramide, and a therapeutic method. More specifically, the present invention relates to a marrow cell proliferation accelerator having potent therapeutic effects on various diseases caused by the damage to marrow cells; a radiation damage protector which has a life-span-increasing effect on those who have been exposed to a lethal dose of radiation, and which is effective for prophylaxis and remedy of side effects caused upon radiotherapy; and a therapeutic agent for thrombocytopenia, capable of increasing the number of blood platelets or inhibiting a reduction the number of blood platelets. Further, the present invention relates to a method of marrow cell proliferation, a method for protecting a human against radiation damage, and a method for the treatment of thrombocytopenia, comprising administering an effective amount of a specific .alpha.-galactosylceramide to a human.
2. Related Art
It is known that marrow cells are damaged and their number is decreased by irradiation with a large dose of radiation, or by administration of a large amount of chemotherapeutic agent.
Further, it is known that hypoplastic anemia, osteomyelodysplasia and the like are diseases caused by a functional disorder (including a decrease in the number) or hypofunction of marrow cells. The marrow cells herein refer to those cells which are present in bone marrow, and include red blood cells, neutrophiles, eosinophils, basophils, monocytes, lymphocytes, and various cells, such as blood platelets, in various differentiated stages.
In order to overcome the damage to marrow cells, which is a cause of the above-described conditions of diseases or diseases, bone marrow transplantation or administration of various hematopoietic factors has been attempted, and, in addition, the exploration of novel marrow-cell-proliferating factors is now being made energetically.
As mentioned above, various diseases or conditions of diseases are caused by the damage to marrow cells. Since a decrease in the number of marrow cells is one of the causes of the diseases, there is a high possibility that a marrow-cell-proliferation-accelerating material can ameliorate the above diseases or conditions of diseases.
.alpha.-rays, .beta.-rays and .gamma.-rays emitted from a radioactive substance, or radiations such as artificially produced potent X-rays, proton rays, neutron rays and electron beams are indispensable for the treatment or diagnosis of diseases such as cancer. However, when more than a permissible dose of radiation is used, or when normal tissues or organs in the body are irradiated during treatment, the numbers of white blood cells, red blood cells and the like are decreased as a side effect of radiation. Therefore, radiotherapy cannot always be conducted completely.
Moreover, irradiation of ultraviolet rays, which is a kind of radiation, also causes various diseases.
Various methods which can prevent such radiation damages and side effects thereof have been studied.
For instance, in a chemical protection method using a medicine, a material capable of revivifying the immunological function of immunocytes which have been inhibited by radiation, for example, cepharanthine or Sonifilan; or an agent for activating respiration of cell tissues, for example, cytochrome C, Solcoselin or adenine have been used. In the present situation the above materials show only a slight effect on preventing the side effects caused by irradiation with radiation.
Further, with respect to radiation damage, a radiation protector containing a processed material of Streptococcus lactis which can eliminate free radicals or active oxygen produced by the ionizing effect of radiation has been proposed (Japanese Laid-Open Patent Publication No. 103023/1987). However, this agent cannot be expected to have excellent effects such as a life-span-increasing effect on those who are exposed to a lethal dose of radiation.
A method in which a material having a macrobiotic effect on those who are exposed to a lethal dose of radiation has been proposed recently. For instance, a method using 2-phenyl-1,2-benzoisoserenazol-3(2H)-on (Japanese Laid-Open Patent Publication No. 135718/1989), a method using a Cimetidine-copper complex (Japanese Laid-Open Patent Publication No. 153640/1989), and a method using a nonapeptide which is known as a serum thymic factor (Japanese Laid-Open Patent Publication No. 36126/1990) have been proposed. However, there are continuous demands for more excellent radioprotective agents.
Blood platelets are a blood cell component which play an important role in the mechanism of hemostasis of the organism. Specific symptoms of thrombocytopenia are hemorrhage and abnormal blood coagulation.
Hereditary thrombocytopenia, idiopathic thrombocytopenic purpura, hypoplastic anemia and the like have been known as thrombocytopenia in which the number of blood platelets decreases. However, a clinical problem in recent years is thrombocytopenia caused as a side effect of a chemotherapeutic agent or radiotherapy used for the treatment of cancer.
All of the chemotherapeutic agents currently used have a potent bone-marrow-suppressive effect, so that administration of such an agent induces a remarkable decrease in the number of white blood cells or blood platelets. There are therefore many cases where the treatment has to be suspended because of this side effect. X-rays or .gamma.-rays, which is used in radiotherapy, also adversely act on hemopoietic tissues such as bone marrow and bring about a drastic decrease in the number of white blood cells or blood platelets as in the case where the chemotherapeutic agent is administered. For this reason, irradiation with radiation is often forced to be discontinued.
Platelet transfusion and bone marrow transplantation are known as therapeutic methods which are often used presently for the treatment of thrombocytopenia caused by the above-described chemotherapy or radiotherapy for cancer.
However, in the case of the above platelet transfusion, it is necessary to conduct transfusion frequently because the life span of white blood cells or blood platelets is short. In addition, the transfusion is attended with the danger of infection by cytomegalovirus or the like. Further, in the case of bone marrow transplantation, it is difficult to find a donor of bone marrow which is compatible with the bone marrow of a patient. Moreover, even after the transplantation of bone marrow, several months are required for the number of blood platelets to be normal.
Under such circumstances, muramyldipeptide derivatives (Laid-Open Publication No. WO 89/01778), human-macrophage-colony-stimulating factors (Japanese Laid-Open Patent Publication No. 207244/1989), interleukin-1 and derivatives thereof (Japanese Laid-Open Patent Publication No. 138224/1990), human BCDF (Japanese Laid-Open Patent Publication No. 101624/1991) and the like are now being developed as therapeutic agents for the above-described thrombocytopenia. However, none of the above agents can sufficiently fulfill the demands. Therefore, more efficacious therapeutic agents for thrombocytopenia are demanded presently.